1. Field of the Invention
The present invention relates in general to an endoscope apparatus, and in particular to an endoscope apparatus provided with a tomographic-image obtaining function for obtaining a tomographic image by scanning an examination area of a subject such as a human body with a signal-wave.
2. Description of the Related Art
There are in wide use in a variety of medical fields electron endoscope apparatuses for observing the interior of a body cavity of a patient, wherein an image formed of the light reflected from the interior of a body cavity of a patient upon the illumination thereof by an illuminating-light is obtained and displayed on a monitor or the like. Further, many endoscope apparatuses are provided with a forceps insertion port, and by inserting a probe therethrough into a body cavity of the patient, a biopsy on the tissue in the body cavity can be performed and treatment administered.
On the other hand, in recent years, efforts to develop a tomographic image obtaining apparatus for obtaining a tomographic image of a subject such as the human body have been advanced. Examples of known tomographic image obtaining apparatuses include: an optical tomographic image obtaining apparatus, which utilizes an optical interference caused by a low-coherence light; and an ultrasound tomographic image obtaining apparatus, which utilizes ultrasonic waves etc.
An OCT (Optical Coherence Tomography) apparatus, which obtains an optical tomographic image of an area of which a measurement is to be taken (hereinafter referred to simply as a measurement area) by measuring the intensity of an interference-light caused by a low-coherence light by heterodyne wave detection, is an example of an optical tomographic image obtaining apparatus; a detailed description thereof can be found in an article in xe2x80x9cO Plus Exe2x80x9d Vol. 21, No. 7, pp. 802-04, by Masamitsu Haruna.
According to the aforementioned OCT apparatus: the low-coherence light emitted from a light source formed of an SLD (Super Luminescent Diode) or the like, is separated into a signal-light and a reference-light; the frequency of the signal-light or the reference-light is slightly shifted by use of a Piezo element or the like; the measurement area is irradiated with the signal-light and interference is caused between the reference-light and the reflected-light reflected from a predetermined depth of said measurement portion; the signal strength of the interference signal produced due to said interference is measured by heterodyne wave detection; and the tomographic data is obtained; wherein, by very slightly moving a movable mirror or the like disposed above the optical path of the reference-light, causing the length of the optical path of the reference-light to change slightly, the length of the optical path of the reference-light and the length of the optical path of the signal-light can be made to be equal, and the data for a predetermined depth of the measurement portion can be obtained. Further, by moving the entry position of the signal-light in slight increments and repeating the measurement operation at each new point, the optical tomographic image of a predetermined scanning area can be obtained.
Because the early diagnosis of the depth of penetration of cancer or the like also becomes possible if an OCT apparatus such as that described above is utilized, efforts to develop methods of obtaining an optical tomographic image of the interior of a body cavity by guiding a signal-light and a reflected-light of the signal-light through an OCT probe that can be inserted into the forceps insertion port of the endoscope apparatus are being advanced. For example, according to an OCT apparatus described in an article in xe2x80x9cOptics Letterxe2x80x9d, Vol. 24, No. 19, pp. 1358-60, by Andrew M Rollin and Rujchai Ung-arunyawee: an OCT probe provided with an optical fiber and a mirror, which is disposed at the distal end of this optical fiber, for reflecting the signal-light at a right angle is inserted through the forceps insertion port of the endoscope apparatus to the interior of a body cavity of a patient; radial scanning is carried out by rotating the mirror disposed at the distal end of the optical fiber; and a radial optical tomographic image, which is an optical tomographic image showing a wall of the interior of the body cavity in round cross-sections, is displayed.
Further, the same as for the OCT apparatus, efforts to develop a probe-shaped apparatus capable of being inserted into the forceps insertion port of an endoscope apparatus for use in conjunction with an ultrasonic tomographic image obtaining apparatus such as that described in xe2x80x9cUltrasound Examination and Diagnostic Techniquesxe2x80x9d, Chapter 6, pp. 126-133 by Hiroaki Okawai, Toyo Press, and the like are being advanced, and the displaying of a tomographic image obtained by these apparatus, together with a reflectance image obtained by an endoscope, is in the process of being realized.
However, in order to employ the endoscope apparatus and probe for obtaining an optical tomographic image described above to obtain an optical tomographic image as described above, because it is necessary to first confirm by use of the endoscope the scanning area of which an optical tomographic image is to be obtained, and to manually guide the probe for obtaining an optical tomographic image to said scanning area. However, because this manual operation to guide the probe is troublesome, there is a problem in that the efficiency of the operation occurring when an optical tomographic image is to be obtained is reduced. Further, there is also a problem in that accurately positioning the distal end of the probe at a desired position is difficult.
The present invention has been developed in consideration of the circumstances described above, and it is a primary object of the present invention to provide an endoscope apparatus provided with an optical tomographic image obtaining function capable of efficiently obtaining an optical tomographic image of a desired scanning area.
The endoscope apparatus according the present invention comprises: a target-subject image obtaining means for projecting an illuminating-light onto the target subject, obtaining an image formed of the reflected-light reflected from the target subject upon the irradiation thereof with the illuminating-light, and forming a target-subject image based on said obtained image formed of said reflected-light; a target-subject image display means for displaying a target-subject image formed by said target-subject image obtaining means; and a tomographic image obtaining means for scanning a scanning area within the target subject with a signal-wave and obtaining a tomographic image of the scanned area; further comprising a position specifying means for specifying one or more desired points on a target-subject image displayed on the target-subject image display means, and a scanning-area setting means for setting a scanning area to be scanned with the signal-wave, based on the point(s) specified by the position specifying means.
Here, the referent of the term xe2x80x9cilluminating-lightxe2x80x9d is not limited to white-light or other visible light, but also includes types of non-visible light such as infrared light and the like. Further, the expression xe2x80x9cforming a target-subject image based on said obtained image formed of said reflected-lightxe2x80x9d can refer to forming a target-subject image by subjecting the image obtained by the image obtaining means to reflectance-image image processing, or forming a target-subject image by subjecting the image obtained by the image obtaining means to any of a number of specialized image-processing processes. As to the specialized image-processing processes, for cases in which the illuminating-light is anon-visible light such as infrared light, etc., an image processing process for converting the image obtained by the image obtaining means to a target-subject image formed of visible light, etc., can be used.
Here, so far as the referent of the phrase xe2x80x9cscanning areaxe2x80x9d is an area capable of being scanned, the shape thereof can be any shape; for example, a line-shaped area on the target subject, or an area on the surface, etc. Further, for cases in which the target subject is an examination area that progresses in a direction moving deeper within a body cavity, etc., a ring-shaped area, or a cylindrical area are included in the referents of xe2x80x9cscanning areaxe2x80x9d.
Further, when xe2x80x9cscanning the scanning areaxe2x80x9d, the format of scanning can be any scanning format. For example, there are radial scanning formats wherein the scanning is performed by rotating a mirror installed at the distal end of a light guiding means for guiding the signal-wave, and linear scanning formats wherein the scanning is performed by moving the irradiation position of the signal-wave in a line form, etc.; in so far as a scanning format is capable of obtaining a tomographic image by use of a signal-wave, said scanning method can be employed. Note that also, any scanning method of scanning the signal-wave may be used; for example, there are scanning methods wherein the scanning is performed by moving the signal-wave emitting end, scanning methods wherein the scanning is performed by reflecting the signal-wave emitted from the emitting end by use of a controllable mirror or the like, of which the reflection direction thereof is capable of being controlled, and so on.
Further, the endoscope apparatus according to the present invention further comprises a tomographic image display means for displaying a tomographic image obtained by the tomographic image obtaining means, which can also be a means for concurrently displaying the target-subject image and the tomographic image.
Still further, the endoscope apparatus according to the present invention may also be an apparatus wherein: the position specifying means is a means for specifying two desired points; the scanning-area setting means is a means for setting as the scanning area an area on the target subject including the points thereon corresponding to the two points specified by the position specifying means; the tomographic image obtaining means is a means for obtaining a plurality of radial tomographic images; further comprising a 3-dimensional tomographic image forming means for forming a 3-dimensional radial tomographic image based on a plurality of radial tomographic images obtained by the tomographic image obtaining means.
Here, xe2x80x9cradial tomographic imagexe2x80x9d refers to a tomographic image obtained by a radial scanning wherein the scanning direction of the signal-wave is rotated within a planar surface in a direction substantially perpendicular to the lengthwise direction of the insertion portion of the endoscope; more specifically, to a tomographic image showing a wall of the interior of the body cavity, into which the insertion portion has been inserted, in round cross-sections.
Further, the expression xe2x80x9csets as the scanning area an area on the target subject containing the points thereon corresponding to the two points specified by the position specifying meansxe2x80x9d refers to, for example, the setting of an area of the body cavity between the radial scanning range including a point on the target subject corresponding to a point specified by the position specifying means and the radial scanning range including another point on the target subject corresponding to another point specified by the position specifying means, as the scanning area.
Still further, the endoscope apparatus according to the present invention may also be an apparatus wherein: the position specifying means is a means for specifying three or more desired points; the scanning-area setting means is a means for setting as the scanning area an area on the target subject enclosed by the points thereon corresponding to the three or more points specified by the position specifying means; the tomographic image obtaining means is a means for obtaining a plurality of linear tomographic images; further comprising a 3-dimensional tomographic image forming means for forming a 3-dimensional linear tomographic image based on a plurality of radial tomographic images obtained by the tomographic image obtaining means.
Here, xe2x80x9clinear tomographic imagexe2x80x9d refers to a tomographic image obtained by a linear scanning wherein the signal-wave is scanned in a line form, including, in addition to standard line-form scanning, cases in which a tomographic image is obtained by a partial radial scanning.
Further, the expression xe2x80x9csets as the scanning area an area on the target subject enclosed by the points thereon corresponding to the three or more points specified by the position specifying meansxe2x80x9d refers to, for example, in a case in which 3 points have been specified by the position specifying means, the setting of an area on the target subject enclosed by a plurality of points thereon corresponding to the three points specified by the position specifying means, as the scanning area.
Still further, when a 3-dimensional tomographic image is to be formed, the endoscope apparatus according to the present invention may also be an apparatus further comprising: a memory means for recording a pixel position on the target-subject image and the relation between said pixel position and a pixel position on a 3-dimensional optical tomographic image; a 3-dimensional position specifying means for specifying a desired point on the 3-dimensional tomographic image displayed on the tomographic image display means; and a 3-dimensional specified point display means for reading out from the memory means the pixel positions of the point specified by the 3-dimensional position specifying means and the point on the target-subject image corresponding thereto, and displaying the specified 3-dimensional position and the point corresponding thereto on the target-subject image. Here, xe2x80x9ca 3-dimensional tomographic imagexe2x80x9d refers to a 3-dimensional radial tomographic image or a 3-dimensional linear tomographic image.
Note that as to the above-described position specifying means and 3-dimensional position specifying means, any means that can specify two desired points can be employed: For example, a pen-type interface for specifying two desired points by touching a display screen therewith; a means for entering the coordinates of two desired points; a mouse that operates as a cursor for inputting two desired points, or the like can be employed there as.
If the aforementioned signal-wave is a low-coherence light, an optical tomographic image obtaining means, which scans the scanning area with the low-coherence light and utilizes the reflected-light reflected from a predetermined depth of the scanning area and a reference-light having a slight difference in frequency with respect to the signal-light, for obtaining an optical tomographic image of the scanning area can be employed. Note that, if the target subject is a living-tissue subject, it is preferable that the low-coherence light is of a wavelength within the 600-1700 nm wavelength range.
If the aforementioned signal-wave is an ultrasonic wave, an ultrasound tomographic image obtaining means, which scans the scanning area with the ultrasonic wave and utilizes the reflected-wave reflected from a predetermined depth of the scanning area, for obtaining an ultrasound tomographic image of the scanning area can be employed. Note that, if the target subject is a living-tissue subject, it is preferable that the frequency of the ultrasonic wave is between 1 MHz and 50 MHz.
According to the endoscope apparatus of the present invention: one or more desired points are specified on a target-subject image displayed on the target-subject image display means, a scanning area to be scanned by the signal-wave is set based on the specified point(s), and the set scanning area is scanned with the signal-wave to obtain a tomographic image thereof; whereby the trouble of having to manually direct the signal-wave to a desired scanning area is eliminated, and because a tomographic image of a desired scanning area can be expediently obtained, a tomographic image of a desired scanning area can be obtained with a high degree of efficiency. Further, a tomographic image of a desired scanning area can be obtained with a high degree of accuracy.
Further, if the target-subject image and the tomographic image are displayed concurrently on the tomographic image display means for displaying a tomographic image, an operator can observe both the target-subject image and the tomographic image concurrently, whereby the overall convenience attained in the practical application of the endoscope apparatus is improved.
Still further, if the endoscope apparatus according to the present invention is an apparatus for setting as the scanning area an area on the target subject including the points thereon corresponding to the two desired points that have been specified, and forming a 3-dimensional radial tomographic image based on a plurality of radial tomographic images obtained by scanning this scanning area with the signal-wave, a 3-dimensional radial tomographic image of a desired area can be obtained with a high degree of efficiency.
In addition, if the endoscope apparatus according to the present invention is an apparatus for setting as the scanning area an area on the target subject enclosed by the points thereon corresponding to the three or more desired points that have been specified, and forming a 3-dimensional linear tomographic image based on a plurality of linear tomographic images obtained by scanning this scanning area with the signal-wave, a 3-dimensional linear tomographic image of a desired area can be obtained with a high degree of efficiency. Further, for cases in which a 3-dimensional tomographic image of a diseased portion that is limited to a localized area, etc., is to be obtained, a 3-dimensional tomographic image of only the area in the vicinity of the diseased portion can be obtained, and a 3-dimensional optical tomographic image is not obtained of unnecessary areas, whereby the radial 3-dimensional optical tomographic image can be obtained with a high degree of efficiency.
If the endoscope apparatus is an apparatus for specifying a desired 3-dimensional point on a 3-dimensional tomographic image, causing the point on the target subject corresponding to the 3-dimensional specified point to be displayed, the operator can easily confirm a desired point on the 3-dimensional optical tomographic image and the point corresponding thereto on the target subject image, whereby the overall convenience attained through the practical application of the endoscope apparatus can be further improved.
For cases in which the signal-wave is a low-coherence light, and the tomographic image obtaining means is an optical tomographic image obtaining means, which scans the scanning area with the low-coherence light and utilizes the reflected-light reflected from a predetermined depth of the scanning area and a reference-light having a slight difference in frequency with respect to the signal-light, for obtaining an optical tomographic image of the scanning area, a high-resolution tomographic image, which has a resolution corresponding to the coherence length of the low-coherence light, can be obtained. Note that, if the target subject is a living-tissue subject and the wavelength of the low-coherence light is within the 600-1700 nm wavelength range, the signal-light exhibits good transmittance and dispersion characteristics with respect to the living-tissue subject.
If the aforementioned signal-wave is an ultrasonic wave, and the tomographic image obtaining means is an ultrasound tomographic image obtaining means, which scans the scanning area with the ultrasonic wave and utilizes the reflected-wave reflected from a predetermined depth of the scanning area, for obtaining an ultrasound tomographic image of the scanning area, because an ultrasonic wave is capable of penetrating to deeper depths of a target subject in comparison to a signal-light or the like, a tomographic image of a deeper portion can be obtained. Note that, if the target subject is a living-tissue subject, and the frequency of the ultrasonic wave is between 1 MHz and 50 MHz, this ultrasonic wave exhibits good reflection characteristics with respect to the living-tissue subject.